Refrigerator having provisions for reducing heat transfer therein



N. E. wlDELL REFRIGERATOR HAVING PROVISIONS FOR Filed Dec. 17. 1947 REDUCING HEAT TRANSFER lTI-IEIREZIN f fa JAW

Patented Dec. 2, 1952 REFRIGERATOR HAVING PROVISIONS FOR REDUCING HEAT TRANSFER THEREIN Nils Erik Widell, Stockholm, Sweden, assignor to Aktiebolaget Elektrolux, Stockholm, Sweden, a corporation of Sweden Application December 17, 1947, Serial No. '792,137 In Sweden December 19, 1946 12 Claims.

particularly concerned with maintaining a storage space of a refrigerator at a low temperature.

It is an object of the invention to provide an improvementl for maintaining a storage space of a refrigerator at a low temperature, particularly to reduce heat transfer into the space.

Another object is to provide an improvement for maintaining a storage space of a refrigerator at a desired low temperature. in order that a larger part of the space will be made available for safely freezing foods and storing frozen food packages Without danger of thawing.

A further object is to elfectively reduce transfer of heat into such a storage space by a closure member which is employed to close an opening provided to gain access into the space.

A still further object of the invention is to provide an improvement in home freezers and similar refrigerators in which a top access opening of a vertically extending storage space is closed by a lid or cover, particularly to reduce the vertical temperature gradient in the storage space.

'Ihe above and other objects and advantages of this invention will be better understood from the following rdescription and accompanying drawing forming a part of this specification, and of which Fig. 1 is a vertical sectional view of a refrigerator embodying the invention; Figs. 2 and 3 are fragmentary vertical sectional views of a refrigerator .like that shown in Fig. 1 illustrating other embodiments of the invention; and Fig. 4 is a fragmentary sectional View taken at line 4 3 of Fig. 3 to show details more clearly.

Referring to Fig. l, the invention is shown in connection with a refrigerator comprising a cabinet I having an inner metal shell II arranged to be supported within an outer metal shell I2 and insulated therefrom with any suitable insulating material III. The inner metal shell II denes a thermally insulated storage space I5 for storing frozen food packages and freezing meat, fruit, vegetables, and other foods as well as fruit juices and other liquids. Access to the storage space I5 is had through the open top thereof which is adapted to be closed by a removable closure member or lid I6 containing a suitable insulating material.

The storage space I5 is arranged tobe cooled by Aa plurality of evaporators I1 and I8 in the form of coils which are disposed about the inner metal shell II, the coil I'I along its length being in good thermal contact with the shell, as by welding, and the coil I8 being spaced from the shell and retained within a plate or shield I9 of annular form which is embedded in` the insulating material I4 between the inner and oute metal shells II and I2, respectively.

The evaporator I'I is connected to a condenser which is in heat exchange relation with a low temperature cooling element 2|, and the evaporator I8 is connected to a condenser 22 which is in heat exchange relation with a higher temperature cooling element 23. Each evaporator and condenser connected thereto forms a'secondary heat transfer system, the evaporators being of the flooded type and located at lower levels than the condensers. The evaporator II and condenser 20 form a closed fluid circuit which is partly filled with a vsuitable volatile uidvthat evaporates in the evaporator I'I and takes up heat thereby producing cold. The vapor rilows from evaporator I1 into condenser 20 in which the vapor is cooled and condensed by cooling element 2|. The liquid condensate formed in condenser 20 returns by gravity through conduit 24 to the evaporator I'I. The evaporator I8 and condenser 22 connected thereto also form a closed iluid circuit partly lled with a volatile fluid which evaporates in the evaporator IB and takes up heat from its surroundings, the vapor thus formed flowing to the condenser 22 in which it is cooled and condensed by cooling element 23 and the condensate returning by gravity through a conduit 2.5 to evaporator I8.

The low and higher temperature cooling elements 2l and 23 may form part of a primary refrigeration system of any suitable type. By Way of example, the primary refrigeration system may be of an absorption type containing an inert gas or pressure equalization agent. InV such a system refrigerant expelled from solution in a generator 26 by heating and liqueed in a condenser 21 flows through cooling elements 23 and 2I in which the liquid evaporates and diffuses in the presence of an inert gas, thereby producing a refrigerating effect for condensing vapor in the condensers 20 and 22.

The resulting gas mixture ofrefrigerant and inert gas fiows from the upper cooling element 23 through a conduit 28, gas heat exchanger 29 and conduit 30 into the lower part of an absorber coil 3l in which refrigerant vapor is absorbed into a liquid absorbent entering through a conduit 32. Inert gas weak in refrigerant is returned to cooling element `2| through gas heat exchanger 29 and a conduit 33. Absorption liquid enriched in the absorber passes into 'an absorber vessel 34 and flows therefrom through a conduit to generator 26 where it is heated and refrigerant vapor 3 again is expelled out of solution. The weakened absorption liquid from which refrigerant has been expelled is conducted from the generator 26 through conduit 32 to again absorb refrigerant vapor.

Since `inert gas-flows first through -co'oling Jelement 2I andthen through coolingfelement 23, the partial vapor pressure of refrigerant vapor is higher in the cooling element 23 than in cooling element 2|, and evaporation .of liquid refrigerant takes place at a higher temperature in the upper cooling element than in the lower cooling element. In order to simplify'the, drawing, therefrigeration system has only"been'shOWn'diagrammatically, systems or" this type being well known which include provisions -'to' insure' upward;` flow of inert gas through the cooling elements 2 I. and 23 in counterfloW to liquid refrigerant.

In the refrigerator .just described the closure member I6 comprises-two sections 36 hinged at underside'o-t-which may -be' provided= a--sea'ling jacket 3'8 formedfo-f rubber, for example,- adapted -to-restI upon the-top-'of the cabinetIIl-ffabout the Aaccess opening Closure members A of fthe type 'f illustrated 1 usually 1 comprise structure providing @spaced` apart inner and outer-walls 39 ande'd, `3respe'ctiv'ely) having a body of ins-ulationJII thereflbetween; and a relatively rigid wall'42A formed .of f material havingpoor .1 thermal' conductivitywhich .@servesas'lthe peripheral edgeportion :and -connests-the inner and-router Walls. Each cover or lid :sectioni' 6 is'v idiagrammatically illustratedl :as shaving afbody oflinsulati'onftherein which isof i 'lconventional and normal depth'or' thickness. The

peripheral edge: portioni42zisgoften referred to as .--.,a,1;tr1m -smpwhiehz maybe anU independentfpart :'rfof theclosure `memberV orv formed integrallywith rthetinner; wall '39,3- for example', :in'which icasethe winner-@walll is :falso formed fof; material, of poor "f ther-mal conductivity.

sWhen the storage-.espace vI5 is: employed to freezefood vandstore:frozenfood packages, it has been :observed .that fthe vertical temperature :gradienttherein is .quite substantial,Y particularly "-'when theastorage spacelisLloaded. In orderi-to mprevent thawing of ...theztop :layer of frozen food "ifpackages :orfotherifrozeni food heldrrthe storage ispaceit has beer'rthe .practice not :to;'.'l1 the :en-

tire space With food therebyz'iproviding-za -rela tively slarge; ain :space'ibetweenxthe top .food'layer .andf'theizclosurermember z I6. vWhile the average wor meanatemperature inzthestora-ge spacerI 5 lcan bermaintanedat; arlower'value.tdenableaflarger adpartofi the spa'cettbezsafelyusedfor: preserving 'rozen; ffoodf packages'r withoutv dangeriof :thawing Menthe-uppermost 'layer of stored' foodsthisfpla ces ffffanzyadditionali:burden '.oni the" refrigeration sapparatusiprovided'tof cool' the storage space. The warmest fair. in :the storage space AI 5 .rises tojthe .ruppervpart' thereof at the regi-on immediately -bef ,low the 'thermally insulated-closure" member .I 6, and it has been found thatthe.'thicknessor f depthof the-insulationprovided in. the Vclosure memberfexercisesvery little innuenceuon they fvertical @temperature gradient iiny the' storage -'fs-nace; that is, the :difference in :temperature at v the, top and Jbottom parts of. the, space. In'accordancewith this inventionfitj has been .io-und that the vertical.temperaturefgradient 'in thezfstorage space-I5 cane-'be substantially d de- :creasedloy reducingthetransfer of heatinto the ='space vbyradiatonxrfrom the underside of: the `r closureimtmiber I6. =As shown in Fig. 2, thismay tf-be-accorrlplished byfproviding 'sheets 43 oi'metalfoil at the underside of the cover I6 which are spaced from the inner walls 39 of the cover sections 36. Each sheet 43 is iixed to the inner Wall 39 of a cover section 36 by screws 44 and held in Xed spaced relation therefrom by hollow spacer members 45. through which` E the-.i screws extend.

` Inthisf'way'an-air gap'i46 isf'formed between the underside of the cover I6 and sheets 43 so that heat radiated from the inner walls 39 toward the sheetsv is re-radiated from the latter back to the f inner-walls. The'sheets 43 of metal foil may be formed of aluminum, artificial resinous compounds or fsimilarVL moisture resistant material f-coatedats'o-pposi-te sides with aluminum foil, or

e `vertical :.tLtem-perature .-vgladen' 'n -l'fTlGfL-Stllage i space. 'i Byrprovidinglithe s'heets'143 "iti-impossible -zftoincreasethe height to :which frozenfood=-pack f ages can bezsafelye'storedinstoragefspac:without any thawing ioffrozenrfood packages'inithe :uppermost layer;Y and"withoutA placing-1an:- addi- :.tionalifburdent onrtheA refrigeration.',apparatus dto maintain '.thestoragespacel at. a lowervmeanffor g, average temperature.

1 *InrFigL 2:is'- illustratedanother embodiment in which thecoveror closuremember IISay is forcen- '.siderably.; fsmaller .fdepthi or :thickness ;L thanI the Y'conventional cover fI 6 diagrammatical-lyli illus- 'trated in'Fig; 1. `v`lfhiletheadepmroftherloodyfof insulatio-nfreta-ined between dhefinnersandfiouter vwalls of fthesgcover; fsections f36aztin' Fig..2i;is. not .-nearlysas: great:Y asrthatin sl'lig..4 1;; nevertheless it :ishighly -eiective andcan fbeiimadesmaller in "ac-cord'wit-h the inventionjby .providing aplurality of -sheets' '43 a: infv yspacedrelationrat the: underside of the-cover 4.16m tofreduceihe'at'transferiinto:the sto-rage space' I 5f duel to radiation. -T-helfs'heets 4#lila are xedi'to theinner walls l39lr'byfscrews"Ma,

. material `having fpoori thermalconducting prop- Vv"crt-ies. V"The .air in .theffgapsbetweenhe sheets 43azand between' the: uppermosti.sheets:and the vvunderside of :the cover -fI-bax-forxnsiv annorezfor less stagnant: air.` body-.which fincrea'ses theA ove-rall .:heat; insulatingi eil-ect. ofithe rcoverrla.

- .Another:embodimentV of: the invention-is zshown rbo'dinrentsin: thatithesheets`f`43b `.provided for fre- 'ducing Itransferof'.he-atiintcystorage :space I'5e1by :radiation'fare :entirely: independent fof. the :cover .ithe'coverfl S'inFig. 1.

i InFig.` 3 itfwillbefseenthat thetsheetsi'bzare in= 'overlappingzrelation'andprovided with pinsy or knobs A'Iztof-acilitate moving each sheet A-I3l1ito- V-ward the Ao-tlfler .tov-gainf-:accessi :intoithe storage space rl 5. `Suitable'zrailsA8 rmay .'bef'fprovidedfat opposing side walls of the s'toragetspace-Ili for f supporting the sheets 43b and guidingtheslatter when moved betweentheirv open '.andfrclosed positions.

."-It Willfbe understoodthat the particular1.1nan ner:in1wh-ichI theisheetii'orrsheets,fof; metal .foil aref.associated/with: a closure :member ,wills afary in; practice dependingfiuponf theidilerent" eorrditions encountered. By way of example and without limitation, the space between the radiation shield or metal foil sheeting and underside of a cover desirably should be in the neighborhood of 4 to 8 mm. when using a conventional cover having a depth of insulation of about 40 rnm. In such case it has been found that the height to which frozen food packages may be safely stored in the storage space can be increased by about 40 to 50 mm. which is approximately the thickness of containers in which most frozen foods are now usually packaged.

When covers are used in which the body of insulation is of less depth or thickness than in conventional covers, a radiation shield formed of a number of spaced apart sheets of metal foil is preferably employed. When such a radiation shield is employed, the distance between the underside of the cover and nearest metal foil, as well as the distance between the several metal foils, desirably should be in a range of about 4 to 8 mm.

In View of the foregoing, it will now be understood that an effective radiation shield has been provided to reduce heat transfer into a storage space of a refrigerator by radiation from an inner wall of a closure member adapted to close an access opening of the space. Since the radiation shield is fixed to the cover only by screws in the embodiments of Figs. 1 and 2 and the radiation shield is entirely independent of the cover in the embodiment of Figs. 3 and 4, it will be apparent that in each embodiment the heat transfer relation of the radiation shield with respect to the body of insulation retained in the cover is relatively small compared to the heat conductive relation of the inner wall of the cover with respect to the outer Wall thereof.

This is so because, while the spaced apart inner and outer walls are connected by a rigid trim strip or other comparable part which is formed of poor heat conducting material, the heat conductive path between the spaced apart wallsv of the cover is substantially greater than the insignificant heat conductive path which is provided in Figs. 1 and 2 by the screws from the insulation within the cover to the metal foil serving as the radiation shield. Since the radiation shield in Figs. 3 and 4 is entirely independent of the vcover and not carried by the latter, the body of insulation therein is thermally segregated from the radiation shield.

Although several embodiments of the invention have been shown and described, such variations and modifications are contemplated as fall within the true spirit and scope of the invention, as pointed out in the following claims:

What is claimed is:

1. In the art of preserving food and the like in a space which is formed with a top access opening and thermally insulated from the surroundings when the access opening is closed, the method which comprises abstracting heat :from said space to effect cooling therein, transferring heat from the surroundings into said space due t0 radiation from a bounding wall surface which is at the access opening and defines the upper extremity of said space when the access opening is closed, reducing such heat transfer by reradiating heat back to said bounding wall surface through a zone of said space from a region thereof which is beneath the closely adjacent to and spaced from said bounding wall surface, and, as the result of cooling effected in said space, inducing natural circulation of air therein including said zone in the extreme upper end thereof, the air in said zone tending to be relatively stagnant and resisting natural circulation of air induced in said space.

2. In the art of preserving food and the like in a space which is formed with a top access opening and thermally insulated from the surroundings when the access opening is closed, the method which comprises abstracting heat from said space to effect cooling therein and induce natural circulation of air, transferring-heat from the surroundings in said space due to radiation from a bounding wall surface which is at the access opening and denes the upper extremity of said space when the access opening is closed, reducing such heat transfer by re-radiating heat back to said bounding wall surface through a zone of said space from a. number of spaced apart regions thereof which are beneath and closely adjacent to and spaced from said bounding wall surface and in poor thermal relation therewith, and, as the result 0f cooling effected in said space, inducing natural circulation of air therein including said zone in the extreme upper end thereof, the air in said zone tending to be relatively stagnant and resisting natural circulation of air induced in said space. f

S. In the art of preserving food and the like in a vertically extending space which is :formed with a top access opening and thermally insulated from the surroundings when the access opening is closed, the method which comprises abstracting heat from said space to effect cooling therein, transferring heat from the surroundings into said space due to radiation from a bounding wall surface which is at the access opening and defines the upper extremity of said space when the access opening is closed, reducing such heat transfer by re-radiating heat back to said bounding wall surface through a zone of said space from a region thereof which is beneath and closely adjacent to and spaced from said bounding wall surface and in poor thermal relation therewith so as to reduce the Vertical temperature gradient in said zone from said bounding Wall surface to said region and, as the result of cooling effected in said space, inducing natural circulation of air therein including said Zone in the upper extremity thereof, the air in said zone tending to be relatively stagnant and resisting natural circulation of air induced in said space.

4. In a refrigerator including a cabinet having a thermally insulated interior or storage space formed with a top access opening and refrigeration apparatus for cooling such space and inducing natural circulation of air in said space, thermally insulated structure for closing the access opening comprising a closure member including spaced apart top and bottom walls having insulation therebetween and a side wall bridging the gap between the spaced apart walls and concealing the insulation from View, said bottom wall constituting the innermost wall surface of the thermally insulated interior when the access opening is completely closed by said thermally insulated structure, a heat radiating shield. external to the walls of said closure member and cooperating therewith for reducing heat transfer into said space by radiation from said bottom wall, said shield being beneath and closely adjacent to and spaced from said bottom wall and in poor heat conductive relation therewith when the top access opening is completely closed by said thermally insulated structure, the space 117 ,fbetween'saidheatsradiatingshield and said ybot- :toxn1'wal1ibeing :located `at the extremeyupper .'part :of'the cabinet interior and in4 communication with air circulatinginsaid storage space.

i 5.#Apparatus asset forth in claim4 in whichY said heat-radiating-shield comprises aluminum sheeting-having Ybright reilecting surfaces.

6.Apparatus-,as set. forth in claim- 4 in which .said heat radiating lshield comprises a plurality 1; `ofspaced apartsheets having bright vreflecting lsurfaces.

'L'Apparats yas, ser forth in ciaimfi inelud- =ing means for securing saidfheatradiating shield r:-to.the-closure member, such means `providing a i; poor. heat-conductive path betweenfsad closure f member and. said shield.

ffApparatus as set forthv inxclaim 4 includw-ing mea-ns independent ,of --saidclosure" member ,.'for`maintaining V-said 1heat.radiati-ng shield in @position beneath andadjacent tov-saidclosure ."member when' theulatter closes the top access opening.

.-9.--Apparatusasset'forth 'in claim 4 in Vwhich r 4saidheat .radiating shield-comprises a plurality oisheets having bright relecting'surfaces, such sheetsA beingi substantially in the same plane and relatively movable with respect-t0A one another in suchplane.

110. In arefrigerator including a/cabinet` havfing ai' thermally insulated interior or -storage space Iprovided with atop access opening and l f meansto-'eifect cooling of'such space, thermally ,rinsulated structure `for closing' the access open- :ingcomprising a closuremember including .1 spacedapart topv'and bottom walls havinginfsulation LtherebetweenA anda sideV wallv bridging 'thefgap between the spaced apart walls and con- Hcealing the insulation from view, said bottom wall constituting thednnermost wall 4surfaceof ,.-the Ythermally insulated interior when the ac'A cess yopening is completely closedby-said ther- .mally.- insulated structure', ar heat radiating shield comprising a layer of material having a surface :for-reducing. heaty transfer into said space by .-r-adiation from the bottomwall-of said closure` f memberg said Ashield beingu positioned beneath .and'closelyadjacentA to--and spaced fromsaid H.bottomwallwhen thev top access opening is v:closedby -said'closure member, the'part of said sspacesbetween'said heatradi'ating shield and said .bottomwall being .in communication vwitlrair circulating in the part of said spacebeneathsaid shield, and supporting. means fonsaid shield to `maintain .the heat conductive relationgofg'said heat radiating shield with' respect :to --saidtclo sure member vinsulation relatively small-com pared tothe Yheat Vconductive relation :of said bottom wall with respect to said top-wall.

11. Apparatus asset forth in claim 10 `in'which said supporting means supports saidfshieldindependently of said closure member.

' 12. In a refrigerator including a cabinet having `a thermally insulated interior or storage space providedfwithy a top access'opening'v and v-means to effect cooling of such-space, thermally 'insulated structure for closing the accessv opening comprising a closure member 'including spaced apart :top Vvand Vbottom walls havingnsulation therebetween and a sidevwall bridging the gap between Vthe' spaced apartY walls and concealing the insulation` from view,'. saidibottom wall constituting the innermost'wall surface-'of the thermally insulated interior when'the access opening is completely closed by said thermally Ainsulated structure; a heat radiating shieldfcomprising a layer ofmaterial having a'surfaoe vfor reducing heat transfer. into -said 'space' byfradialtion from the bottom wall of said lclosuremember, said shield being positioned Abeneath: and closely adjacent to and spacedv -from'said bottomwallV when the top Y'access opening is closed byl said closure member, vand means. xed to and carried 'by said closure 'member 'forrsupporting said shield to lmaintain the heat conductive-relation of said heat radiating shieldwith respect to said closure member insulation relatively: small compared to the -h'eat conductive-frelation offsaid bottom wall with respect to said 'top-wall.

. NILS ERIK -WIDELIL ...REFERENCES CITED The .following references are of 'recordin'the le of-this patent:

'UNITED STATES PATENTS 

